Biochar is a new word to describe fine-grained, highly porous charcoal made from biological material (biomass), high in organic carbon. This excludes fossil fuel products, geological carbon and industrial synthetics (plastics).

A primary purpose for biochar is as soil enhancement to help retain nutrients and water, and habitat for the soil food web. This includes food-producing farm soils, so careful specifications are needed to define materials suitable for this use.

2. Why should I be interested in biochar?

Biochar is a key element in a new carbon-negative strategy to resolve several critical current ecological, economic and energy challenges. Properly made and used, biochar can mitigate climate change and other environmental effects:

Biochar is produced when biomass is heated to 500 degrees with a minimum or absence of oxygen. Normal combustion oxidizes biomass into alkali ash, plus steam, CO2, other gases and vapors. If air is excluded, oxygen for combustion is stripped out of the biomass, which is reduced to carbon-carbon bonds of char.

Charcoal was made for centuries around the world by simple methods with few or no tools. Small batches can be homemade with simple bucket or barrel burners. Modern gasification and pyrolysis technology uses controlled combustion in air-tight retorts to process tons of biomass into energy, gases and liquids.

4. Can biochar support sustainable agriculture?

Biochar enhances soil in numerous ways. Its use in soil is new, exciting and not well understood yet. Biochar isnít a fertilizer, or food source for plants or microbes. Understanding its action requires a paradigm shift from chemical views to emerging 21st Century insights into the biology of the soil food web.

Recently, scientists in Amazon rainforest found that 4,000 years ago tribes used biochar to create highly fertile terra preta. Japanese used biochar in soil successfully for centuries before it was displaced by industrial chemicals.

Even better, soils retain nutrients and sustain productivity better than soils without biochar. Plants grow well in soil with 9% biochar, at less cost, increased yield, and sustain this greater production longer with less fertilizer. Food from those soils has higher nutritional balance, density and quality.

Biocharís sponge-like capacity to hold water and nutrients in its micropores make it an excellent addition in potting soil mixes.

7. Does biochar replace compost?

Biochar is different than conventional organic matter created by decay of plant and animal waste. While biochar is a substrate for microbial cultures, fresh biochar is bone dry and sterile, and must be inoculated with compost, compost tea or other cultures.

8. Can biochar reduce greenhouse gas levels?

Carbon in biochar resists degradation, decay and digestion, and can sequester carbon in soils hundreds to thousands of years.

Photosynthesis unites CO2 with water to make carbohydrates, or sugar. If biochar is made in a burner, some carbon returns to the air as CO2, but 20 to 60% of the carbon remains as biochar.

Thus, biochar in soil is a true carbon-negative strategy.
Biochar remains in soil far longer than other organic matter, such as compost, plant residue or manure that oxidize quickly. Biochar is one of our few ways to permanently sequester carbon.

Robert Brown at Iowa State University, with a $1.8-million USDA grant, calculates corn stalk pyrolysis into biochar on a 250-hectare farm can sequester 1,900 tons of carbon a year.

NASA climate scientist James HansenĎs August 2008 paper estimates that applied worldwide, soil sequestration by biochar can lower CO2 by ~8ppm in 50 years.

In soil, biochar improves fertility to stimulate greater growth, which then fixes more CO2 into biomass. So each yearís harvest of biomass is larger, to convert to more biofuel and biochar—building fertility each year—Natureís positive feedback cycle.

Biochar by modern controlled pyrolysis is an approved Clean Development Mechanism in the UN Framework Convention on Climate Change to avoid methane from biomass decay.

Currently, biochar earns no credit on any carbon exchange as a way to sequester carbon. However, as 2008 ends, proposals were presented at a series of international climate deliberations.

9. Can biochar produce renewable energy?

Biomass is the worldís third largest fuel, after coal and oil. Most biomass is woody matter, green wastes, crop residues, food processing wastes (eg. rice husks). Current biomass-to-energy technology is at best carbon neutral, and isnít sustainable, since harvests deplete nutrients, reducing fertility and productivity.

Pyrolysis making biochar also produces energy. As biomass breaks down into char, hydrogen, methane and other hydrocarbons are released and captured to refine into renewable fuels. Energy produced making biochar can be turned into space heat, electricity, reformed into ethanol or ultra-clean diesel.

One ton of biomass can equal 5.5 barrels of oil. Pyrolysis uses wastes, and about half the original carbon and most minerals are returned to the soil, where they support sustainable, biological fertility. Biochar sequestration is our best chance to turn energy production into a carbon-negative industry.

National Renewable Energy Lab research concluded that each gigajoule of hydrogen produced stores 112 kg of CO2 in soil.